Răspuns :
2n+1 / 2n+5
n=1
2x1+1 /2x1+5=2+1/2+5= 3/7
n=2
2x2+1 /2x2+5 = 4+1 /4+5 = 5/9
n=3
2x3+1 /2x3+5= 6+1 /6+5 = 7/11
n=4
2x4+1 /2x4+5 = 8+1 /8+5= 9/13
n=1 ; 2 ; 3 ; 4..............
n=1
2x1+1 /2x1+5=2+1/2+5= 3/7
n=2
2x2+1 /2x2+5 = 4+1 /4+5 = 5/9
n=3
2x3+1 /2x3+5= 6+1 /6+5 = 7/11
n=4
2x4+1 /2x4+5 = 8+1 /8+5= 9/13
n=1 ; 2 ; 3 ; 4..............